Forming metal components by hydraulic shock



July 16, 1968 H. A. FEATHER 3,392,561

FORMING METAL COMPONENTS BY HYDRAULIC SHOCK Filed Nov. 22. 1965 20 Fly. 2 25 l J 2/ l9 /9 /7 .25 i I z 1 fla k 20 5 k 20 I2 18 gg Fig.3 ,4

J INVENTOR L Harry A. Feafher ATTORNEY United States PatentOflice 3,392,561 Patented July 16, 1968 ABSTRACT OF THE DISCLOSURE An apparatus for forming sheet material wherein the sheet material is clamped between a cover plate and a die member and wherein hydraulic pressure admitted through the cover plate both forces the stock against the die member to form the same and bulges the cover outwardly. Impact pressure above the .yield strength of the material is applied to the bulged cover plate and is transmitted to the sheet material by the hydraulic fluid. a

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

This invention relates to a method and apparatus for forming sheet material and more particularly to means for forming the sheet material in a mold by application of fluid pressure and an impact force thereto.

Commercially available reflectors for illuminating an aeroballistic range are usually of unacceptable quality and those reflectors of acceptable quality are usually prohibitive in cost. In the past, aluminum reflectors, made from a spinning and polishing process were used, but, proved to be too expensive and of poor quality. There existed a need for an inexpensive means of forming light metal sections of the desired quality. The present invention fulfills this need.

It is therefore an object of the present invention to provide a device which will form sheet material by application of fluid pressure and an impact force applied thereto.

Another object of the invention is to provide a device which will deform when fluid pressure is applied thereto and which will form sheet metal upon the impact of a force to the deformed portion.

A further object of the invention is the provision of a forming mold that will deform when fluid pressure is applied thereto and which will form sheet metal, upon the impact of a force, above the yield strength of the sheet metal, to the deformed portion.

A further object of the invention is the provision of a forming mold which produces a reflector of high quality at low cost.

Briefly described, the invention consists of a mold body or die having the desired contour formed therein, and a removable cover having valved filling and venting ports. Means clamp the sheet to be formed between the cover and the body and form a high pressure seal around the edge. The body is further provided with vent holes to allow the air under the sheet to escape during the formation process. The actual forming is accomplished in the following manner:

(a) Fluid is pumped into the mold between the cover and the sheet of metal until all of the entrapped air is forced through the vent. The vent valve is then closed. The pumping is then continued until the sheet metal has seated on the mold and the cover has bulged upwardly. The fill port valve is then closed.

(b) A weight is then dropped on the cover to produce an impact pressure above the "yield strength of the sheet metal to form an accurately shaped piece.

' Other objects, adva'ntagesand new features of the present invention will become apparent from a reading of the following detailed description when taken with the accompanying drawing wherein:

FIG. 1 is atop view of an assembled mold;

FIG. 2 is a view in vertical section, taken along lines 22 of FIG. 1, illustrating theinterior of the mold; and v FIG. 3 is an enlarged view of the sealing structure between the body and the cover of the mold.

Referring now to FIGS. 1 and 2, a circular disc cover tending side wall 12 and a front wall 16 with a concave contour 14 formed therein. A plurality of vent passages 20 ,are formed in the body 11 to connect the interior of the concave portion 14 to the atmosphere through the side wall 12. A work piece 17, preferably of sheet metal, is clamped between the cover 15 and body 11, in any suitable manner, as by cap screws 19 which pass through the cover 15 into threaded engagement with holes 18 in body 11.

A high pressure seal is formed around the edge of the sheet metal 17. An embodiment of this seal is shown in FIG. 3, wherein the raised lips 23 on the body 11 coact with the groove 24 on the cover 15 so as to clamp the sheet metal 17 therebetween and to press the sheet into the groove 24 to further enhance the sealing action around the edge.

Fluid pressure is applied to the space or pressure chamber 26 formed in cover 15 above the clamped work piece 17, through the fill port 21, in cover 15, by means of a pump and valve arrangement (not shown). Entrapped air between the cover 15 and work piece 17 is forced out through vent port 22, by the fluid pumped through the fill port 21. A valve (not shown) controls the flow of air through the vent port 22. Pumping is continued until the sheet metal work piece 17 has been seated on the concave contour 14, as shown at 27 in FIG. 2, and the cover plate 15 has been bulged outwardly, as shown in phantom line in FIG. 2. A weight 25 having a predetermined mass is then dropped on the bulging cover 15 to finally form the work piece.

The actual forming of the sheet metal is accomplished by clamping the work piece 17 between the cover 15 and body 11 by means of the cap screws 19 and then pumping fluid through the fill port 21 into the space 26 in mold 10 between the cover 15 and the work piece 17 until all of the entrapped air is forced through the vent port 22. The vent valve is then closed and the pumping continued causing the work piece 17 to be seated on the mold contour 14, as shown at 27 in FIG. 2 and forcing air under the work piece 17 through the vent ports 20 in the body 11. Pumping is finally stopped and the'fill port valve closed when the cover plate 15 has bulged outwardly as shown in phantom lines in FIG. 2. A sufliciently heavy weight 25 is then dropped on the bulging cover to produce an impact pressure above the yield strength of the work piece to be formed. The strengths for various materials which may be used in the mold 10 and work piece 17 are readily available. It is necessary to select conditions which will exceed the strength of the material to be formed and not exceed the yield strength of the mold. In computing these conditions it is known that the average force of the blow (impact pressure) is equal to the weight times the distance dropped divided by the distance in which the weight is stopped.

The above method and apparatus takes advantage of the inertia of: relatively heavy body sections to offset the extreme pressures which can be developed by impact. The fluid evenly distributes the impact pressures over the surface of the material to be formed.

Obviously, many modifications and variations of the invention will be suggested to those skilled in the art by the above description. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as herein specifically described.

What is claimed is:

1. An apparatus for forming articles from sheet material comprising:

a die member having one face thereof contoured to the predetermined shape of the formed article;

a deformable cover member having a pressure chamber;

coacting means on said die member and said cover member for both clamping the sheet material therebetween and forming a high pressure seal around said chamber;

means on said cover member communicating with said chamber for admitting fluid pressure to said chamber to 'urge the sheet material against said die mem- 25 ber and to bulge the cover member outwardly;

venting means on said cover member communicating with said chamber for allowing entrapped air to escape from said chamber;

means associated with said cover member for impacting said bulged cover member and producing an impact pressure above the yield strength of the sheet material.

2. The apparatus as defined in claim 1 wherein said coacting means includes a raised lip about the die member and a groove on said cover member for mating engagement with said raised lip.

3. The apparatus as defined in claim 2 wherein said means for impacting said bulged cover member includes a movable weight of predetermined mass which is dropped a predetermined distance to said bulged cover member.

References Cited UNITED STATES PATENTS 1,561,312 11/1925 Cutler et al. 72-60 1,625,914 4/1927 Seibt 72-60 2,399,775 5/1946 Whistler et al. 72-60 2,615,411 10/1952 Clevenger et al. 726O 3,149,596 9/1964 De Vlieg et al. 7260 RICHARD J. HERBST, Primary Examiner. 

